408 research outputs found
Smart Power Grid Synchronization With Fault Tolerant Nonlinear Estimation
Effective real-time state estimation is essential for smart grid synchronization, as electricity demand continues to grow, and renewable energy resources increase their penetration into the grid. In order to provide a more reliable state estimation technique to address the problem of bad data in the PMU-based power synchronization, this paper presents a novel nonlinear estimation framework to dynamically track frequency, voltage magnitudes and phase angles. Instead of directly analyzing in abc coordinate frame, symmetrical component transformation is employed to separate the positive, negative, and zero sequence networks. Then, Clarke\u27s transformation is used to transform the sequence networks into the αβ stationary coordinate frame, which leads to system model formulation. A novel fault tolerant extended Kalman filter based real-time estimation framework is proposed for smart grid synchronization with noisy bad data measurements. Computer simulation studies have demonstrated that the proposed fault tolerant extended Kalman filter (FTEKF) provides more accurate voltage synchronization results than the extended Kalman filter (EKF). The proposed approach has been implemented with dSPACE DS1103 and National Instruments CompactRIO hardware platforms. Computer simulation and hardware instrumentation results have shown the potential applications of FTEKF in smart grid synchronization
Comparing Kalman Filters and Observers for Power System Dynamic State Estimation with Model Uncertainty and Malicious Cyber Attacks
Kalman filters and observers are two main classes of dynamic state estimation
(DSE) routines. Power system DSE has been implemented by various Kalman
filters, such as the extended Kalman filter (EKF) and the unscented Kalman
filter (UKF). In this paper, we discuss two challenges for an effective power
system DSE: (a) model uncertainty and (b) potential cyber attacks. To address
this, the cubature Kalman filter (CKF) and a nonlinear observer are introduced
and implemented. Various Kalman filters and the observer are then tested on the
16-machine, 68-bus system given realistic scenarios under model uncertainty and
different types of cyber attacks against synchrophasor measurements. It is
shown that CKF and the observer are more robust to model uncertainty and cyber
attacks than their counterparts. Based on the tests, a thorough qualitative
comparison is also performed for Kalman filter routines and observers.Comment: arXiv admin note: text overlap with arXiv:1508.0725
Combating False Reports for Secure Networked Control in Smart Grid via Trustiness Evaluation
Smart grid, equipped with modern communication infrastructures, is subject to
possible cyber attacks. Particularly, false report attacks which replace the
sensor reports with fraud ones may cause the instability of the whole power
grid or even result in a large area blackout. In this paper, a trustiness
system is introduced to the controller, who computes the trustiness of
different sensors by comparing its prediction, obtained from Kalman filtering,
on the system state with the reports from sensor. The trustiness mechanism is
discussed and analyzed for the Linear Quadratic Regulation (LQR) controller.
Numerical simulations show that the trustiness system can effectively combat
the cyber attacks to smart grid.Comment: It has been submitted to IEEE International Conference on
Communications (ICC
Smart Grid State Estimation with PMUs Time Synchronization Errors
We consider the problem of PMU-based state estimation combining information
coming from ubiquitous power demand time series and only a limited number of
PMUs. Conversely to recent literature in which synchrophasor devices are often
assumed perfectly synchronized with the Coordinated Universal Time (UTC), we
explicitly consider the presence of time-synchronization errors in the
measurements due to different non-ideal causes such as imperfect satellite
localization and internal clock inaccuracy. We propose a recursive Kalman-based
algorithm which allows for the explicit offline computation of the expected
performance and for the real-time compensation of possible frequency mismatches
among different PMUs. Based on the IEEE C37.118.1 standard on PMUs, we test the
proposed solution and compare it with alternative approaches on both synthetic
data from the IEEE 123 node standard distribution feeder and real-field data
from a small medium voltage distribution feeder located inside the EPFL campus
in Lausanne.Comment: 10 page, 7 figure
Intelligent approach for processmodelling and optimization on electrical dischargemachining of polycrystalline diamond
Polycrystalline diamond (PCD) is increasingly becomes an important material used in the industry for cutting tools of difficult-to-machine materials due to its excellent characteristics such as hardness, toughness and wear resistance. However, its applications are restricted because of the PCD material is difficult to machine. Therefore, electrical discharge machining (EDM) is an ideal method suitable for PCD materials due to its non-contact process nature. The performance of EDM, however, is significantly influenced by its process parameters and type of electrode. In this study, soft computing technique was utilized to optimize the performance of the EDM in roughing condition for eroding PCD with copper tungsten or copper nickel electrode. Central composite design with five levels of three machining parameters viz. peak current, pulse interval and pulse duration has been used to design the experimental matrix. The EDM experiment was conducted based on the design experimental matrix. Subsequently, the effectiveness of EDM on shaping PCD with copper tungsten and copper nickel was evaluated in terms of material removal rate (MRR) and electrode wear rate (EWR). It was found that copper tungsten electrode gave lower EWR, in comparison with the copper nickel electrode. The predictive model of radial basis function neural network (RBFNN) was developed to predict the MRR and EWR of the EDM process. The prominent predictive ability of RBFNN was confirmed as the prediction errors in terms of mean-squared error were found within the range of 6.47E−05 to 7.29E−06. Response surface plot was drawn to study the influences of machining parameters of EDM for shaping PCD with copper tungsten and copper nickel. Subsequently, moth search algorithm (MSA) was used to determine the optimal machining parameters, such that the MRR was maximized and EWR was minimized. Based on the obtained optimal parameters, confirmation test with the absolute error within the range of 1.41E−06 to 5.10E−05 validated the optimization capability of MSA
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